How do I stop overthinking this?

For context: me and my crush have been close best friends since last year. He very evidently cares for me and unless my judgement is entirely wrong, I think he might have some feelings for me too.

Now, I know this will sound obsessive, but I got his latest post on my feed on Instagram (I'm on his close friends too if that matters?), and looked through it.

When I checked the comments, up to now the profiles I'd see I either couldn't distinguish or were guys, but this time it was a girl. It's perfectly fine for him to have girl friends obviously, but this girl he follows and he liked both of her comments (as he does with every comment he gets).

I've been overthinking this for the past couple of hours. What if she's his ex? What if she's that girl he used to crush on? What if she's just a better friend to him than I am? What if she's funnier? Is she prettier? I never comment on his posts so that made me feel even more insecure.

Any advice on how I can stop this? I know it's dumb but it's genuinely slowly driving me mad.